This invention relates to the synthesis of light hydrocarbons to higher hydrocarbons, including gasoline, at conversion levels that compliment secondary product utilization. The process uses unsynthesized light hydrocarbons, together with oxides of carbon produced as secondary products, to make methanol. The methanol and/or the higher hydrocarbons may then be used to make gasoline or ethylene.
Previous work on gasoline synthesis has concentrated on methane, because methane is a chemical in plentiful supply, natural gas being principally composed of methane. One known way of producing gasoline from methane, originally developed by Mobil Oil Company, is to first reform desulfurized natural gas to form hydrogen, carbon monoxide and carbon dioxide, otherwise known as synthesis gas or syngas. Methanol is then synthesized from the syngas by well established low pressure techniques. Gasoline is made by passing the methanol over a suitable catalyst, as disclosed in U.S. Pat. Nos. 3,894,107, 3,931,349 and related patents.
Another route, developed by the Atlantic Richfield Company (ARCO), involves first synthesizing higher olefins from methane, using a suitable oxidizing catalyst as disclosed in U.S. Pat. No. 4,777,313 and the patents listed therein. Some gasoline is produced by this synthesis, and the lower hydrocarbons produced by the synthesis can also be converted to gasoline. The main disadvantage of this method is that, at commercially acceptable selectivity, the methane conversion is relatively low. The solution adopted by ARCO was to recycle the unconverted methane, requiring a very large reactor/regenerator system. Further, the large amount of carbon dioxide produced in the synthesis was unused, being vented to the atmosphere. This means that much of the carbon from the methane is not converted to something useful. Further, the release of large amounts of carbon dioxide into the atmosphere could be environmentally detrimental.